Crosslinked polyamide compositions are known in the art (See, W. Feng et al., “Radiation Physics and Chemistry”, 63, pp. 493-496 (2002)). Japanese published application 59-012936A2 describes a crosslinked polyamide resin obtained by exposing a polyamide resin containing a crosslinker to a radiation beam. The resin can be free of glass fiber, and a flame retardant or filler can be incorporated into the resin.
Japanese published application 02-196856A2 describes a crosslinking flame-resistant polyamide composition prepared by compounding a polyamide with a brominated, crosslinkable styrenic resin and a multifunctional monomer and, if necessary, a flame resistance auxiliary. The multifunctional monomer can be triallyl cyanurate or triallyl isocyanu rate. The polyamide resin composition is crosslinked with an ionizing radiation.
Japanese published application 2003-327726A2 describes a resin composition comprising a polyamide resin, a multifunctional monomer, a bromine-based flame retardant, an antimony-based flame retardant auxiliary, and hydrotalcite. The crosslinked polyamide resin molding is formed by irradiation crosslinking with an ionizing radiation.
Crosslinked polyamide materials can be used as a cost-effective replacement for thermosets or high temperature resistant polymers. The materials can be used for articles and parts for electronics and electrical applications where good short-term heat resistance is needed and are which are not met by regular flame retardant polyamide compositions. Exemplary applications include contact holders in electrical contactors and lead free soldering connectors. These applications often require the composition to possess properties such as high short-term heat resistance, good flame retardant properties, good mechanical properties, and good arc tracking resistance. Although there are known crosslinked polyamide materials, none have been able to meet all of the stringent requirements needed for electronic applications.
Moreover, flame retardants can differ widely in their flow properties and thus, can influence the formulation flow properties. The type of flame retardants used can also impact the electrical properties of a polymer formulation. Polymer formulations with higher comparative tracking index (CTI) values permits thinner wall thickness, but thinner wall applications necessitate superior flow properties during compounding.
Accordingly, there remains a need in the art for halogen-free flame retardant crosslinked polymer compositions that exhibit good flame retardant properties, good electrical performance such as arc tracking resistance, while at the same time retaining good mechanical properties. Accordingly, these needs, and others are met by the present invention.